The present paper reports a double pass forward superfluorescent fiber source （SFS）, which uses a length of large mode area double cladding ytterbium doped fiber as gain medium. The maximum output power of this SFS is 341 mW. With the output power between 201 and 341 mW, the 3dB bandwidth of this SFS was more than 80 nm. This is the widest 3 dB bandwidth obtained from ytterbium doped SFS. The output power of the SFS linearly increased with the increment of the pump source injected current. It’s output power is not very high, but under normal circumstances, it could meet the needs of the SFS. From the energy level structure of ytterbium ions and the absorption cross-section/emission cross section of ytterbium ions in quartz substrate, the physical mechanisms responsible for superfluorescence were analyzed. This double-cladding ytterbium-doped superfluorescent fiber laser benefits from the superfluorescence radiation near 1 025 and 1 075 nm, so the superfluorescence with 3 dB bandwidth reaching up to 80 nm could be obtained.